/*
 * EAP-IKEv2 server (RFC 5106)
 * Copyright (c) 2007, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "eap_i.h"
#include "eap_common/eap_ikev2_common.h"
#include "ikev2.h"


struct eap_ikev2_data {
        struct ikev2_initiator_data ikev2;
        enum { MSG, FRAG_ACK, WAIT_FRAG_ACK, DONE, FAIL } state;
        struct wpabuf *in_buf;
        struct wpabuf *out_buf;
        size_t out_used;
        size_t fragment_size;
        int keys_ready;
        u8 keymat[EAP_MSK_LEN + EAP_EMSK_LEN];
        int keymat_ok;
};


static const u8 * eap_ikev2_get_shared_secret(void *ctx, const u8 *IDr,
                                              size_t IDr_len,
                                              size_t *secret_len)
{
        struct eap_sm *sm = ctx;

        if (IDr == NULL) {
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: No IDr received - default "
                           "to user identity from EAP-Identity");
                IDr = sm->identity;
                IDr_len = sm->identity_len;
        }

        if (eap_user_get(sm, IDr, IDr_len, 0) < 0 || sm->user == NULL ||
            sm->user->password == NULL) {
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: No user entry found");
                return NULL;
        }

        *secret_len = sm->user->password_len;
        return sm->user->password;
}


static const char * eap_ikev2_state_txt(int state)
{
        switch (state) {
        case MSG:
                return "MSG";
        case FRAG_ACK:
                return "FRAG_ACK";
        case WAIT_FRAG_ACK:
                return "WAIT_FRAG_ACK";
        case DONE:
                return "DONE";
        case FAIL:
                return "FAIL";
        default:
                return "?";
        }
}


static void eap_ikev2_state(struct eap_ikev2_data *data, int state)
{
        wpa_printf(MSG_DEBUG, "EAP-IKEV2: %s -> %s",
                   eap_ikev2_state_txt(data->state),
                   eap_ikev2_state_txt(state));
        data->state = state;
}


static void * eap_ikev2_init(struct eap_sm *sm)
{
        struct eap_ikev2_data *data;

        data = os_zalloc(sizeof(*data));
        if (data == NULL)
                return NULL;
        data->state = MSG;
        data->fragment_size = IKEV2_FRAGMENT_SIZE;
        data->ikev2.state = SA_INIT;
        data->ikev2.peer_auth = PEER_AUTH_SECRET;
        data->ikev2.key_pad = (u8 *) os_strdup("Key Pad for EAP-IKEv2");
        if (data->ikev2.key_pad == NULL)
                goto failed;
        data->ikev2.key_pad_len = 21;

        /* TODO: make proposals configurable */
        data->ikev2.proposal.proposal_num = 1;
        data->ikev2.proposal.integ = AUTH_HMAC_SHA1_96;
        data->ikev2.proposal.prf = PRF_HMAC_SHA1;
        data->ikev2.proposal.encr = ENCR_AES_CBC;
        data->ikev2.proposal.dh = DH_GROUP2_1024BIT_MODP;

        data->ikev2.IDi = (u8 *) os_strdup("hostapd");
        data->ikev2.IDi_len = 7;

        data->ikev2.get_shared_secret = eap_ikev2_get_shared_secret;
        data->ikev2.cb_ctx = sm;

        return data;

failed:
        ikev2_initiator_deinit(&data->ikev2);
        os_free(data);
        return NULL;
}


static void eap_ikev2_reset(struct eap_sm *sm, void *priv)
{
        struct eap_ikev2_data *data = priv;
        wpabuf_free(data->in_buf);
        wpabuf_free(data->out_buf);
        ikev2_initiator_deinit(&data->ikev2);
        os_free(data);
}


static struct wpabuf * eap_ikev2_build_msg(struct eap_ikev2_data *data, u8 id)
{
        struct wpabuf *req;
        u8 flags;
        size_t send_len, plen, icv_len = 0;

        wpa_printf(MSG_DEBUG, "EAP-IKEV2: Generating Request");

        flags = 0;
        send_len = wpabuf_len(data->out_buf) - data->out_used;
        if (1 + send_len > data->fragment_size) {
                send_len = data->fragment_size - 1;
                flags |= IKEV2_FLAGS_MORE_FRAGMENTS;
                if (data->out_used == 0) {
                        flags |= IKEV2_FLAGS_LENGTH_INCLUDED;
                        send_len -= 4;
                }
        }

        plen = 1 + send_len;
        if (flags & IKEV2_FLAGS_LENGTH_INCLUDED)
                plen += 4;
        if (data->keys_ready) {
                const struct ikev2_integ_alg *integ;
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Add Integrity Checksum "
                           "Data");
                flags |= IKEV2_FLAGS_ICV_INCLUDED;
                integ = ikev2_get_integ(data->ikev2.proposal.integ);
                if (integ == NULL) {
                        wpa_printf(MSG_DEBUG, "EAP-IKEV2: Unknown INTEG "
                                   "transform / cannot generate ICV");
                        return NULL;
                }
                icv_len = integ->hash_len;

                plen += icv_len;
        }
        req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_IKEV2, plen,
                            EAP_CODE_REQUEST, id);
        if (req == NULL)
                return NULL;

        wpabuf_put_u8(req, flags); /* Flags */
        if (flags & IKEV2_FLAGS_LENGTH_INCLUDED)
                wpabuf_put_be32(req, wpabuf_len(data->out_buf));

        wpabuf_put_data(req, wpabuf_head_u8(data->out_buf) + data->out_used,
                        send_len);
        data->out_used += send_len;

        if (flags & IKEV2_FLAGS_ICV_INCLUDED) {
                const u8 *msg = wpabuf_head(req);
                size_t len = wpabuf_len(req);
                ikev2_integ_hash(data->ikev2.proposal.integ,
                                 data->ikev2.keys.SK_ai,
                                 data->ikev2.keys.SK_integ_len,
                                 msg, len, wpabuf_put(req, icv_len));
        }

        if (data->out_used == wpabuf_len(data->out_buf)) {
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Sending out %lu bytes "
                           "(message sent completely)",
                           (unsigned long) send_len);
                wpabuf_free(data->out_buf);
                data->out_buf = NULL;
                data->out_used = 0;
        } else {
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Sending out %lu bytes "
                           "(%lu more to send)", (unsigned long) send_len,
                           (unsigned long) wpabuf_len(data->out_buf) -
                           data->out_used);
                eap_ikev2_state(data, WAIT_FRAG_ACK);
        }

        return req;
}


static struct wpabuf * eap_ikev2_buildReq(struct eap_sm *sm, void *priv, u8 id)
{
        struct eap_ikev2_data *data = priv;

        switch (data->state) {
        case MSG:
                if (data->out_buf == NULL) {
                        data->out_buf = ikev2_initiator_build(&data->ikev2);
                        if (data->out_buf == NULL) {
                                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Failed to "
                                           "generate IKEv2 message");
                                return NULL;
                        }
                        data->out_used = 0;
                }
                /* pass through */
        case WAIT_FRAG_ACK:
                return eap_ikev2_build_msg(data, id);
        case FRAG_ACK:
                return eap_ikev2_build_frag_ack(id, EAP_CODE_REQUEST);
        default:
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Unexpected state %d in "
                           "buildReq", data->state);
                return NULL;
        }
}


static Boolean eap_ikev2_check(struct eap_sm *sm, void *priv,
                               struct wpabuf *respData)
{
        const u8 *pos;
        size_t len;

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_IKEV2, respData,
                               &len);
        if (pos == NULL) {
                wpa_printf(MSG_INFO, "EAP-IKEV2: Invalid frame");
                return TRUE;
        }

        return FALSE;
}


static int eap_ikev2_process_icv(struct eap_ikev2_data *data,
                                 const struct wpabuf *respData,
                                 u8 flags, const u8 *pos, const u8 **end)
{
        if (flags & IKEV2_FLAGS_ICV_INCLUDED) {
                int icv_len = eap_ikev2_validate_icv(
                        data->ikev2.proposal.integ, &data->ikev2.keys, 0,
                        respData, pos, *end);
                if (icv_len < 0)
                        return -1;
                /* Hide Integrity Checksum Data from further processing */
                *end -= icv_len;
        } else if (data->keys_ready) {
                wpa_printf(MSG_INFO, "EAP-IKEV2: The message should have "
                           "included integrity checksum");
                return -1;
        }

        return 0;
}


static int eap_ikev2_process_cont(struct eap_ikev2_data *data,
                                  const u8 *buf, size_t len)
{
        /* Process continuation of a pending message */
        if (len > wpabuf_tailroom(data->in_buf)) {
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Fragment overflow");
                eap_ikev2_state(data, FAIL);
                return -1;
        }

        wpabuf_put_data(data->in_buf, buf, len);
        wpa_printf(MSG_DEBUG, "EAP-IKEV2: Received %lu bytes, waiting for %lu "
                   "bytes more", (unsigned long) len,
                   (unsigned long) wpabuf_tailroom(data->in_buf));

        return 0;
}


static int eap_ikev2_process_fragment(struct eap_ikev2_data *data,
                                      u8 flags, u32 message_length,
                                      const u8 *buf, size_t len)
{
        /* Process a fragment that is not the last one of the message */
        if (data->in_buf == NULL && !(flags & IKEV2_FLAGS_LENGTH_INCLUDED)) {
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: No Message Length field in "
                           "a fragmented packet");
                return -1;
        }

        if (data->in_buf == NULL) {
                /* First fragment of the message */
                data->in_buf = wpabuf_alloc(message_length);
                if (data->in_buf == NULL) {
                        wpa_printf(MSG_DEBUG, "EAP-IKEV2: No memory for "
                                   "message");
                        return -1;
                }
                wpabuf_put_data(data->in_buf, buf, len);
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Received %lu bytes in first "
                           "fragment, waiting for %lu bytes more",
                           (unsigned long) len,
                           (unsigned long) wpabuf_tailroom(data->in_buf));
        }

        return 0;
}


static int eap_ikev2_server_keymat(struct eap_ikev2_data *data)
{
        if (eap_ikev2_derive_keymat(
                    data->ikev2.proposal.prf, &data->ikev2.keys,
                    data->ikev2.i_nonce, data->ikev2.i_nonce_len,
                    data->ikev2.r_nonce, data->ikev2.r_nonce_len,
                    data->keymat) < 0) {
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Failed to derive "
                           "key material");
                return -1;
        }
        data->keymat_ok = 1;
        return 0;
}


static void eap_ikev2_process(struct eap_sm *sm, void *priv,
                              struct wpabuf *respData)
{
        struct eap_ikev2_data *data = priv;
        const u8 *start, *pos, *end;
        size_t len;
        u8 flags;
        u32 message_length = 0;
        struct wpabuf tmpbuf;

        pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_IKEV2, respData,
                               &len);
        if (pos == NULL)
                return; /* Should not happen; message already verified */

        start = pos;
        end = start + len;

        if (len == 0) {
                /* fragment ack */
                flags = 0;
        } else
                flags = *pos++;

        if (eap_ikev2_process_icv(data, respData, flags, pos, &end) < 0) {
                eap_ikev2_state(data, FAIL);
                return;
        }

        if (flags & IKEV2_FLAGS_LENGTH_INCLUDED) {
                if (end - pos < 4) {
                        wpa_printf(MSG_DEBUG, "EAP-IKEV2: Message underflow");
                        eap_ikev2_state(data, FAIL);
                        return;
                }
                message_length = WPA_GET_BE32(pos);
                pos += 4;

                if (message_length < (u32) (end - pos)) {
                        wpa_printf(MSG_DEBUG, "EAP-IKEV2: Invalid Message "
                                   "Length (%d; %ld remaining in this msg)",
                                   message_length, (long) (end - pos));
                        eap_ikev2_state(data, FAIL);
                        return;
                }
        }
        wpa_printf(MSG_DEBUG, "EAP-IKEV2: Received packet: Flags 0x%x "
                   "Message Length %u", flags, message_length);

        if (data->state == WAIT_FRAG_ACK) {
                if (len != 0) {
                        wpa_printf(MSG_DEBUG, "EAP-IKEV2: Unexpected payload "
                                   "in WAIT_FRAG_ACK state");
                        eap_ikev2_state(data, FAIL);
                        return;
                }
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Fragment acknowledged");
                eap_ikev2_state(data, MSG);
                return;
        }

        if (data->in_buf && eap_ikev2_process_cont(data, pos, end - pos) < 0) {
                eap_ikev2_state(data, FAIL);
                return;
        }
                
        if (flags & IKEV2_FLAGS_MORE_FRAGMENTS) {
                if (eap_ikev2_process_fragment(data, flags, message_length,
                                               pos, end - pos) < 0)
                        eap_ikev2_state(data, FAIL);
                else
                        eap_ikev2_state(data, FRAG_ACK);
                return;
        } else if (data->state == FRAG_ACK) {
                wpa_printf(MSG_DEBUG, "EAP-TNC: All fragments received");
                data->state = MSG;
        }

        if (data->in_buf == NULL) {
                /* Wrap unfragmented messages as wpabuf without extra copy */
                wpabuf_set(&tmpbuf, pos, end - pos);
                data->in_buf = &tmpbuf;
        }

        if (ikev2_initiator_process(&data->ikev2, data->in_buf) < 0) {
                if (data->in_buf == &tmpbuf)
                        data->in_buf = NULL;
                eap_ikev2_state(data, FAIL);
                return;
        }

        switch (data->ikev2.state) {
        case SA_AUTH:
                /* SA_INIT was sent out, so message have to be
                 * integrity protected from now on. */
                data->keys_ready = 1;
                break;
        case IKEV2_DONE:
                if (data->state == FAIL)
                        break;
                wpa_printf(MSG_DEBUG, "EAP-IKEV2: Authentication completed "
                           "successfully");
                if (eap_ikev2_server_keymat(data))
                        break;
                eap_ikev2_state(data, DONE);
                break;
        default:
                break;
        }

        if (data->in_buf != &tmpbuf)
                wpabuf_free(data->in_buf);
        data->in_buf = NULL;
}


static Boolean eap_ikev2_isDone(struct eap_sm *sm, void *priv)
{
        struct eap_ikev2_data *data = priv;
        return data->state == DONE || data->state == FAIL;
}


static Boolean eap_ikev2_isSuccess(struct eap_sm *sm, void *priv)
{
        struct eap_ikev2_data *data = priv;
        return data->state == DONE && data->ikev2.state == IKEV2_DONE &&
                data->keymat_ok;
}


static u8 * eap_ikev2_getKey(struct eap_sm *sm, void *priv, size_t *len)
{
        struct eap_ikev2_data *data = priv;
        u8 *key;

        if (data->state != DONE || !data->keymat_ok)
                return NULL;

        key = os_malloc(EAP_MSK_LEN);
        if (key) {
                os_memcpy(key, data->keymat, EAP_MSK_LEN);
                *len = EAP_MSK_LEN;
        }

        return key;
}


static u8 * eap_ikev2_get_emsk(struct eap_sm *sm, void *priv, size_t *len)
{
        struct eap_ikev2_data *data = priv;
        u8 *key;

        if (data->state != DONE || !data->keymat_ok)
                return NULL;

        key = os_malloc(EAP_EMSK_LEN);
        if (key) {
                os_memcpy(key, data->keymat + EAP_MSK_LEN, EAP_EMSK_LEN);
                *len = EAP_EMSK_LEN;
        }

        return key;
}


int eap_server_ikev2_register(void)
{
        struct eap_method *eap;
        int ret;

        eap = eap_server_method_alloc(EAP_SERVER_METHOD_INTERFACE_VERSION,
                                      EAP_VENDOR_IETF, EAP_TYPE_IKEV2,
                                      "IKEV2");
        if (eap == NULL)
                return -1;

        eap->init = eap_ikev2_init;
        eap->reset = eap_ikev2_reset;
        eap->buildReq = eap_ikev2_buildReq;
        eap->check = eap_ikev2_check;
        eap->process = eap_ikev2_process;
        eap->isDone = eap_ikev2_isDone;
        eap->getKey = eap_ikev2_getKey;
        eap->isSuccess = eap_ikev2_isSuccess;
        eap->get_emsk = eap_ikev2_get_emsk;

        ret = eap_server_method_register(eap);
        if (ret)
                eap_server_method_free(eap);
        return ret;
}
